V.S. Senashenko

On the possibility of investigating atomic autoionizing states in coincidence experiments

Abstract The possibility of investigating atomic autoionizing states in coincidence experiments on inelastic scattering of fast particles is discussed. The calculations have been performed for the (2s 2p)1P(−)-state of helium.

Lifetimes of the metastable states of the lithium-like ions

Abstract The lifetime of the (1s2s2p)4 P 5 2 state of the lithium-like ions from Li to O5+ has been calculated using the screened Coulomb functions of the bound electrons. The lifetimes of the (1s2s2p)4 P 1 2 , 3 2 states in these ions have been evaluated. The theoretical results are compared with experiment [1,2].

The effect of the electron bound state structure on ionization cross sections in atomic collisions

The cross sections for loss of 1s-, 2s- and 2p-electrons by various hydrogen-like ions during their encounters with H and He atoms and atomic nuclei have been calculated in the Born approximation with the use of the sum rule and compared with each other. The dependence of these cross sections on the structure of the wavefunctions of the electron bound state is investigated. Comparison is made between theory and experiment.

On the effect of the electron bound state structure on ionization cross sections in atomic collisions

Abstract The cross sections for 1s- and 2s-electron loss by various hydrogen-like ions colliding with H and He have been calculated and compared. An exact expression is given for the square of the matrix element of the 2s-electron transition to the continuum states.

Resonance photoabsorption of the helium atom in the vicinity of the (3s3p) 1P resonance

Excitation energies and eigen widths of the 1P(-) low-lying autoionising levels of the helium atom converging to the n=3 state of the He+ ion have been obtained in the diagonalisation approximation of Balashov et al., (1970). Calculations were made of all the experimentally obtained parameters which determine the photoabsorption cross section in the vicinity of the (3s3p) 1P resonance. From comparison of the calculation results with the experimental data and with other calculations, a conclusion is drawn about the applicability of the diagonalisation approximation for the calculation of the total photoabsorption cross sections in which the direct coupling between open channels is neglected.

On the shape of the (2s2)1S resonance in the spectra of electrons ejected from He atoms during their encounters with fast electrons and protons

Some aspects of the theoretical description of the intensity and shape of resonances observed in the spectra of electrons ejected from atoms by fast electrons and protons are discussed. Numerical calculations have been performed for the (2s2)1S resonance of helium atoms. Dependences of the resonance intensity and shape on the collision kinematics, i.e. incident-particle energy and electron ejection angle, have been obtained. The considerable variations revealed in the character of the resonance asymmetry with varying ejection angle are associated with a strong interference between separate components of the transition amplitude.

On the possibility of using the Cauchy distribution for extracting the parameters of autoionizing states from experimental data

Abstract The possibility of using the Cauchy distribution for extracting the parameters of autoionizing states from experimental data is discussed. Relations for determining the resonance parameters have been obtained.

Possibilities of diagonalization method for calculating the atomic system resonances

Abstract The photoionization of He below n = 2 threshold has been calculated within the framework of the diagonalization method.

About the influence of two-step excitation of autoionization states on resonance profiles in H++He collisions

The authors discuss the influence of the two-step excitation mechanism on the shape of autoionization resonances in electron emission spectra of helium. The parameters of the (2s2)1S resonance, allowing for correlation and the two-step excitation mechanism, with the inclusion of the Coulomb interaction in the final state in the direct and resonance ionization amplitudes, have been calculated for ionization of helium by intermediate-energy protons.

Charge sign dependence of autoionization resonance profiles produced by protons and antiprotons

Abstract Strong sign charge dependence for the autoionization resonance shape in electron emission spectra has been found for ionization of helium by protons and antiprotons. It appears to be more pronounced at small ejection angles and should be observed experimentally. Moreover ionization collisions with antiprotons can be used for spectroscopic measurements of autoionization resonance characteristics at those electron ejection angles.